The present invention relates to azaindole compounds, compositions, and medicaments thereof, as well as methods of treatments therefor. These azaindoles inhibit Aurora kinase.
Protein kinases catalyze the phosphorylation of hydroxylic amino acid side chains in proteins by the transfer of the γ-phosphate of ATP-Mg2+ to form a mono-phosphate ester of serine, threonine or tyrosine. Studies have shown that protein kinases are key regulators of many cell functions, including signal transduction, transcriptional regulation, cell motility and cell division. Several oncogenes have also been shown to encode protein kinases, suggesting that kinases may play a role in oncogenesis.
The protein kinase family of enzymes is typically classified into two main subfamilies: protein tyrosine kinases and protein serine/threonine kinases, based on the amino acid residue they phosphorylate. Aberrant protein serine/threonine kinase activity has been implicated or is suspected in a number of pathologies such as rheumatoid arthritis, psoriasis, septic shock, bone loss, cancers and other proliferative diseases. Tyrosine kinases play an equally important role in cell regulation. These kinases include several receptors for molecules such as growth factors and hormones, including epidermal growth factor receptor, insulin receptor and platelet derived growth factor receptor. Studies have indicated that many tyrosine kinases are transmembrane proteins with their receptor domains located on the outside of the cell and their kinase domains on the inside. Accordingly, both kinase subfamilies and their signal transduction pathways are important targets for drug design.
Since its discovery in 1997, the mammalian Aurora family of serine/threonine kinases has been closely linked to tumorigenesis. The three known mammalian family members, Aurora-A (“2”), B (“1”) and C (“3”), are highly homologous proteins responsible for chromosome segregation, mitotic spindle function and cytokinesis. Aurora expression is low or undetectable in resting cells, with expression and activity peaking during the G2 and mitotic phases in cycling cells. In mammalian cells proposed substrates for the Aurora A and B kinases include histone H3, CENP-A, myosin II regulatory light chain, protein phosphatase 1, TPX2, INCENP, p53 and survivin, many of which are required for cell division.
The Aurora kinases have been reported to be over-expressed in a wide range of human tumors. Elevated expression of Aurora-A has been detected in colorectal, ovarian and pancreatic cancers and in invasive duct adenocarcinomas of the breast. High levels of Aurora-A have also been reported in renal, cervical, neuroblastoma, melanoma, lymphoma, pancreatic and prostate tumor cell lines. Amplification/over-expression of Aurora-A is observed in human bladder cancers and amplification of Aurora-A is associated with aneuploidy and aggressive clinical behavior. Moreover, amplification of the Aurora-A locus (20q13) correlates with poor prognosis for patients with node-negative breast cancer. In addition, an allelic variant, isoleucine at amino acid position 31, is reported to be a low-penetrance tumor-susceptibility gene and displays greater transforming potential than the phenylalanine-31 variant and is associated with increased risk for advanced and metastatic disease. Like Aurora A, Aurora-B is also highly expressed in multiple human tumor cell lines, including leukemic cells. Levels of Aurora-B increase as a function of Duke's stage in primary colorectal cancers. Aurora-C, which is normally only found in germ cells, is also over-expressed in a high percentage of primary colorectal cancers and in a variety of tumor cell lines including cervical adenocarinoma and breast carcinoma cells.
It has been suggested that in vitro an inhibitor of Aurora kinase activity disrupts mitosis causing cell cycle defects and eventual cell death. Therefore, in vivo, an Aurora kinase inhibitor should slow tumor growth and induce regression. For example, Hauf et al. describe an Aurora B inhibitor, Hesperadin, that causes defects in chromosomal segregation and a block in cytokinesis, thereby resulting in polyploidy [Hauf, S et al. JCB 161(2), 281-294 (2003)]. Ditchfield et al. have described an equipotent inhibitor of Aurora A and B (ZM447439) that causes defects in chromosome alignment, chromosome segregation and cytokinesis [Ditchfield, C. et al., JCB 161(2), 267-280 (2003)]. Furthermore, the authors show that proliferating cells, but not cell-cycle arrested cells, are sensitive to the inhibitor. Efficacy of a potent Aurora A and B inhibitor in mouse and rat xenograft models was recently reported [Harrington, E. A. et al., Nature Medicine 10(3), 262-267, (2004)]. These results demonstrate that inhibition of Aurora kinases can provide a therapeutic window for the treatment of proliferative disorders such as cancer (see Nature, Cancer Reviews, Vol. 4, p 927-936, December 2004, for a review by N. Keen and S Taylor). In view of the teachings of the art, there is a need for the discovery of kinase activity inhibitors, in particular, compounds that inhibit the activity of Aurora kinases.